Through study on the influencing factors in coking waste water treatment process, AAO waste water treatment process is optimized, the anaerobic tank has been modified.

The anaerobic tank which is set before the UNITANK process improves nitrogen and phosphorus removal efficiency efficiently.

Secondly, denitrification rate is improved because the oxygen pool is before the anaerobic pool and the anaerobic denitrifying bacteria readily biodegradable COD as carbon source;